Systems and Methods for Spinal Fusion

ABSTRACT

A system and method for spinal fusion comprising a spinal fusion implant of non-bone construction releasably coupled to an insertion instrument dimensioned to introduce the spinal fusion implant into any of a variety of spinal target sites.

CROSS-REFERENCE TO RELATED APPLICATION

This application is continuation of U.S. patent application Ser. No.13/440,062 filed Apr. 5, 2012, which is a continuation of U.S. patentapplication Ser. No. 13/079,645 filed Apr. 4, 2011, which iscontinuation of U.S. patent application Ser. No. 11/093,409 filed Mar.29, 2005 (now U.S. Pat. No. 7,918,891), which claims the benefit of thefiling date under 35 USC 119(e) of United States Provisional Applicationentitled “Systems and Methods for Spinal Fusion,” Ser. No. 60/557,536filed Mar. 29, 2004, the entire contents of these prior applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates generally to spinal surgery and, moreparticularly, to a system and method for spinal fusion comprising aspinal fusion implant of non-bone construction releasably coupled to aninsertion instrument dimensioned to introduce the spinal fusion implantinto any of a variety of spinal target sites.

II. Discussion of the Prior Art

Currently there are nearly 500,000 spine lumbar and cervical fusionprocedures performed each year in the United States. Such procedures arecommonly performed to correct problems, such as chronic back or neckpain, which result from degenerated intervertebral discs or trauma.Generally, spinal fusion procedures involve removing some or all of thediseased or damaged disc, and inserting one or more intervertebralimplants into the resulting disc space. Introducing the intervertebralimplant serves to restore the height between adjacent vertebrae (“discheight”), which reduces if not eliminates neural impingement commonlyassociated with a damaged or diseased disc.

Autologous bone grafts are widely used intervertebral implant for lumbarfusion. Autologous bone grafts are obtained by harvesting a section ofbone from the iliac crest of the patient and thereafter implanting thearticle of autologous bone graft to effect fusion. While generallyeffective, the use of autologous bone grafts suffers certain drawbacks.A primary drawback is the morbidity associated with harvesting theautologous graft from the patient's iliac crest. Another relateddrawback is the added surgical time required to perform thebone-harvesting.

Allograft bone grafts have been employed with increased regularity in aneffort to overcome the drawbacks of autologous bone grafts. Allograftbone grafts are harvested from cadaveric specimens, machined, andsterilized for implantation. While allograft bone grafts eliminate themorbidity associated with iliac crest bone harvesting, as well asdecrease the overall surgical time, they still suffer certain drawbacks.A primary drawback is supply constraint, in that the tissue banks thatprocess and produce allograft bone implants find it difficult toforecast allograft given the inherent challenges in forecasting thereceipt of cadavers. Another related drawback is that it is difficult tomanufacture the allograft with consistent shape and strengthcharacteristics given the variation from cadaver to cadaver.

The present invention is directed at overcoming, or at least improvingupon, the disadvantages of the prior art.

SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of the prior art byproviding a spinal fusion system and related methods involving the useof a spinal fusion implant of non-bone construction. The non-boneconstruction of the spinal fusion implant of the present inventionovercomes the drawbacks of the prior art in that it is not supplylimited (as with allograft) and does not require harvesting bone fromthe patient (as with autograft). The spinal fusion implant of thepresent invention may be comprised of any suitable non-bone composition,including but not limited to polymer compositions (e.g.poly-ether-ether-ketone (PEEK) and/or poly-ether-ketone-ketone (PEKK)),ceramic, metal or any combination of these materials.

The spinal fusion implant of the present invention may be provided inany number of suitable shapes and sizes depending upon the particularsurgical procedure or need. The spinal fusion implant of the presentinvention may be dimensioned for use in the cervical and/or lumbar spinewithout departing from the scope of the present invention. For lumbarfusion, the spinal fusion implant of the present invention may bedimensioned, by way of example only, having a width ranging between 9and 18 mm, a height ranging between 8 and 16 mm, and a length rangingbetween 25 and 45 mm. For cervical fusion, the spinal fusion implant ofthe present invention may be dimensioned, by way of example only, havinga width about 11 mm, a height ranging between 5 and 12 mm, and a lengthabout 14 mm.

The spinal fusion implant of the present invention may be provided withany number of additional features for promoting fusion, such asapertures extending between the upper and lower vertebral bodies whichallow a boney bridge to form through the spinal fusion implant of thepresent invention. Such fusion-promoting apertures may be dimensioned toreceive any number of suitable osteoinductive agents, including but notlimited to bone morphogenic protein (BMP) and bio-resorbable polymers,including but not limited to any of a variety of poly(D,L-lactide-co-glycolide) based polymers. The spinal fusion implant ofthe present invention is preferably equipped with one or more lateralopenings which aid it provides in visualization at the time ofimplantation and at subsequent clinical evaluations.

The spinal fusion implant of the present invention may be provided withany number of suitable anti-migration features to prevent spinal fusionimplant from migrating or moving from the disc space after implantation.Suitable anti-migration features may include, but are not necessarilylimited to, angled teeth formed along the upper and/or lower surfaces ofthe spinal fusion implant and/or spike elements disposed partiallywithin and partially outside the upper and/or lower surfaces of thespinal fusion implant. Such anti-migration features provide theadditional benefit of increasing the overall surface area between thespinal fusion implant of the present invention and the adjacentvertebrae, which promotes overall bone fusion rates.

The spinal fusion implant of the present invention may be provided withany number of features for enhancing the visualization of the implantduring and/or after implantation into a spinal target site. According toone aspect of the present invention, such visualization enhancementfeatures may take the form of the spike elements used foranti-migration, which may be manufactured from any of a variety ofsuitable materials, including but not limited to a metal, ceramic,and/or polymer material, preferably having radiopaque characteristics.The spike elements may also take any of a variety of suitable shapes,including but not limited to a generally elongated element disposedwithin the implant such that the ends thereof extend generallyperpendicularly from the upper and/or lower surfaces of the implant. Thespike elements may each comprise a unitary element extending throughupper and lower surfaces or, alternatively, each spike element maycomprise a shorter element which only extends through a single surface(that is, does not extend through the entire height of the implant). Inany event, when the spike elements are provided having radiodensecharacteristics and the implant is manufactured from a radiolucentmaterial (such as, by way of example only, PEEK and/or PEKK), the spikeelements will be readily observable under X-ray or fluoroscopy such thata surgeon may track the progress of the implant during implantationand/or the placement of the implant after implantation.

The spinal implant of the present invention may be introduced into aspinal target site through the use of any of a variety of suitableinstruments having the capability to releasably engage the spinalimplant. In a preferred embodiment, the insertion instrument permitsquick, direct, accurate placement of the spinal implant of the presentinvention into the intervertebral space. According to one embodiment,the insertion instrument includes a threaded engagement elementdimensioned to threadably engage into a receiving aperture formed in thespinal fusion implant of the present invention. According to anotherembodiment, the insertion instrument includes an elongate fork memberand a generally tubular lock member.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a perspective view of a spinal fusion system of the presentinvention, including a lumbar fusion implant releasably coupled to aninsertion instrument according to one embodiment of the presentinvention;

FIG. 2 is a perspective view of the lumbar fusion implant of FIG. 1,illustrating (among other things) fusion apertures extending between topand bottom surfaces, a plurality of visualization apertures extendingthrough the side walls, and a variety of anti-migration featuresaccording to one embodiment of the present invention;

FIG. 3 is a top view of the lumbar fusion implant of FIG. 1,illustrating (among other things) the fusion apertures and theanti-migration features according to one embodiment of the presentinvention;

FIG. 4 is a side view of the lumbar fusion implant of FIG. 1,illustrating (among other things) the visualization apertures, theanti-migration feature, and a receiving aperture for releasably engagingthe insertion instrument of FIG. 1 according to one embodiment of thepresent invention;

FIG. 5 is an end view of the lumbar fusion implant of FIG. 1,illustrating (among other things) the receiving aperture formed in theproximal end, the anti-migration features, and the visualizationapertures according to one embodiment of the present invention;

FIG. 6 is an enlarged side view of the lumbar fusion implant of FIG. 1releasably coupled to the distal end of the insertion instrument of FIG.1 according to one embodiment of the present invention;

FIG. 7 is a perspective view of the insertion instrument of FIG. 1 in afully assembled form according to one embodiment of the presentinvention;

FIG. 8 is an enlarged perspective view of the distal region of theinsertion instrument of

FIG. 1 according to one embodiment of the present invention;

FIG. 9 is a perspective exploded view of the insertion instrument ofFIG. 1, illustrating the component parts of the insertion instrumentaccording to one embodiment of the present invention;

FIG. 10 is a perspective view of a spinal fusion system of the presentinvention, including a cervical fusion implant releasably coupled to acervical insertion instrument according to one embodiment of the presentinvention;

FIG. 11 is a perspective view of the proximal side of the cervicalfusion implant of FIG. 10, illustrating (among other things) fusionapertures extending between top and bottom surfaces, a plurality ofvisualization apertures extending through the lateral walls, a pluralityof receiving apertures, and a variety of anti-migration featuresaccording to one embodiment of the present invention;

FIG. 12 is a perspective view of the distal side cervical fusion implantof FIG. 10, illustrating (among other things) the visualizationapertures and anti-migration features;

FIG. 13 is a top view of the cervical fusion implant of FIG. 10,illustrating (among other things) the fusion apertures andanti-migration features according to one embodiment of the presentinvention;

FIG. 14 is a side view of the cervical fusion implant of FIG. 10,illustrating (among other things) the visualization apertures, theanti-migration features, and one of two receiving apertures provided inthe proximal end for releasably engaging the cervical insertioninstrument of FIG. 10 according to one embodiment of the presentinvention;

FIG. 15 is a perspective view of the cervical fusion implant of thepresent invention just prior to attachment to the cervical insertiondevice according to one embodiment of the present invention;

FIG. 16 is a perspective view of the insertion instrument of FIG. 10 ina fully assembled form according to one embodiment of the presentinvention;

FIG. 17 is a perspective exploded view of the insertion instrument ofFIG. 10, illustrating the component parts of the insertion instrumentaccording to one embodiment of the present invention;

FIGS. 18 and 19 are perspective and side views, respectively,illustrating the “enhanced visualization” feature of the presentinvention as employed within a lumbar fusion implant according to oneembodiment of the present invention;

FIGS. 20 and 21 are perspective and side views, respectively,illustrating the “enhanced visualization” feature of the presentinvention as employed within a lumbar fusion implant according to oneembodiment of the present invention; and

FIGS. 22 and 23 are perspective and side views, respectively,illustrating the “enhanced visualization” feature of the presentinvention as employed within a cervical fusion implant according to oneembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The system to facilitate bone fusion and relatedmethods disclosed herein boasts a variety of inventive features andcomponents that warrant patent protection, both individually and incombination.

FIG. 1 illustrates, by way of example only, a spinal fusion system 5 forperforming spinal fusion between adjacent lumbar vertebrae, including anexemplary spinal fusion implant 10 and an exemplary insertion instrument20 provided in accordance with the present invention. The spinal fusionimplant 10 may be comprised of any suitable non-bone composition havingsuitable radiolucent characteristics, including but not limited topolymer compositions (e.g. poly-ether-ether-ketone (PEEK) and/orpoly-ether-ketone-ketone (PEKK)) or any combination of PEEK and PEKK.The spinal fusion implant 10 of the present invention may bedimensioned, by way of example only, having a width ranging between 9and 18 mm, a height ranging between 8 and 16 mm, and a length rangingbetween 25 and 45 mm.

As will be described in detail below, the insertion instrument 20 isconfigured to releasably maintain the exemplary spinal fusion implant 10in the proper orientation during insertion into a lumbar disc space andthereafter release to deposit the implant 10. The exemplary spinalfusion implant 10, having been deposited in the disc space, facilitatesspinal fusion over time by maintaining a restored disc height as naturalbone growth occurs through and/or past the implant 10, resulting in theformation of a boney bridge extending between the adjacent vertebralbodies. The implant 10 is particularly suited for introduction into thedisc space via a lateral (trans-psoas) approach to the spine, but may beintroduced in any of a variety of approaches, such as posterior,anterior, antero-lateral, and postero-lateral, without departing fromthe scope of the present invention (depending upon the sizing of theimplant 10).

The spinal fusion implant 10 of the present invention may be providedwith any number of additional features for promoting fusion, such asapertures 2 extending between the upper and lower vertebral bodies whichallow a boney bridge to form through the spinal fusion implant 10.According to a still further aspect of the present invention, thisfusion may be facilitated or augmented by introducing or positioningvarious osteoinductive materials within the apertures 2 and/or adjacentto the spinal fusion implant 10. Such osteoinductive materials may beintroduced before, during, or after the insertion of the exemplaryspinal fusion implant 10, and may include (but are not necessarilylimited to) autologous bone harvested from the patient receiving thespinal fusion implant 10, bone allograft, bone xenograft, any number ofnon-bone implants (e.g. ceramic, metallic, polymer), bone morphogenicprotein, and bio-resorbable compositions, including but not limited toany of a variety of poly (D,L-lactide-co-glycolide) based polymers.

The spinal fusion implant 10 of the present invention is preferablyequipped with one or more visualization apertures 4 situated along thelateral sides, which aid in visualization at the time of implantationand at subsequent clinical evaluations. More specifically, based on thegenerally radiolucent nature of the implant 10, the visualizationapertures 4 provide the ability to visualize the interior of the implant10 during X-ray and/or other suitable imaging techniques which areundertaken from the side (or “lateral”) perspective of the implant 10.If fusion has taken place, the visualization apertures 4 will provide amethod for the surgeon to make follow up assessments as to the degree offusion without any visual interference from the spinal fusion implant10. Further, the visualization apertures 4 will provide an avenue forcellular migration to the exterior of the spinal fusion implant 10. Thusthe spinal fusion implant 10 will serve as additional scaffolding forbone fusion on the exterior of the spinal fusion implant 10.

FIGS. 2-5 depict various embodiments of the exemplary spinal fusionimplant 10. Some common attributes are shared among the variousembodiments. More specifically, each spinal fusion implant 10 has a topsurface 31, a bottom surface 33, lateral sides 14, a proximal side 22,and a distal side 16. In one embodiment, the top and bottom surfaces 31,33 are generally parallel. It can be appreciated by one skilled in theart that although the surfaces 31, 33 are generally parallel to oneanother, they may be provided in any number of suitable shapes,including but not limited to concave and/or convex. When provided asconvex shapes, the top and bottom surfaces 31, 33 may better match thenatural contours of the vertebral end plates. Although not shown, itwill be appreciated that the top and bottom surfaces 31, 33 may beangled relative to one another to better match the natural lordosis ofthe lumbar and cervical spine or the natural kyphosis of the thoracicspine.

The exemplary spinal fusion implant 10 also preferably includesanti-migration features designed to increase the friction between thespinal fusion implant 10 and the adjacent contacting surfaces of thevertebral bodies so as to prohibit migration of the spinal fusionimplant 10 after implantation. Such anti-migration features may includeridges 6 provided along the top surface 31 and/or bottom surface 33.Additional anti-migration features may also include a pair of spikeelements 7 disposed within the proximal region of the implant 10, a pairof spike elements 8 disposed within the distal region of the implant 10,and a pair of spike elements 9 disposed within the central region of theimplant 10. Spike elements 7, 8, 9 may extend from the top surface 31and/or bottom surface 33 within the respective proximal, distal andcentral regions of the implant 10. The spike elements 7, 8, 9 may bemanufactured from any of a variety of suitable materials, including butnot limited to a metal, ceramic, and/or polymer material, preferablyhaving radiopaque characteristics. The spike elements 7, 8, 9 may alsotake any of a variety of suitable shapes, including but not limited to agenerally elongated element disposed within the implant 10 such that theends thereof extend generally perpendicularly from the upper and/orlower surfaces 31, 33 of the implant 10. As best appreciated in FIG. 4,the spike elements 7, 8, 9 may each comprise a unitary element extendingthrough upper and lower surfaces 31, 33. Alternatively, each spikeelement 7, 8, 9 may comprise a shorter element which only extendsthrough a single surface 31, 33 (that is, does not extend through theentire height of the implant 10). In any event, when the spike elements7, 8, 9 are provided having radiodense characteristics and the implant10 is manufactured from a radiolucent material (such as, by way ofexample only, PEEK and/or PEKK), the spike elements 7, 8, 9 will bereadily observable under X-ray or fluoroscopy such that a surgeon maytrack the progress of the implant 10 during implantation and/or theplacement of the implant 10 after implantation.

The spinal fusion implant 10 has two large fusion apertures 2, separatedby a medial support 50, extending in a vertical fashion through the topsurface 31 and bottom surface 33. The fusion apertures 2 functionprimarily as an avenue for bony fusion between adjacent vertebrae. Thefusion apertures 2 may be provided in any of a variety of suitableshapes, including but not limited to the generally rectangular shapebest viewed in FIG. 3, or a generally circular, oblong and/or triangularshape or any combination thereof. The spinal fusion implant 10 may havea plurality of visualization apertures 4 which allow a clinician to makevisual observations of the degree of bony fusion un-obscured by thelateral side 14 to facilitate further diagnosis and treatment. Thevisualization apertures 4 may be provided in any of a variety ofsuitable shapes, including but not limited to the generally oblong shapebest viewed in FIG. 4, or a generally circular, rectangular and/ortriangular shape or any combination thereof.

The spinal fusion implant 10 may be provided with any number of suitablefeatures for engaging the insertion instrument 20 without departing fromthe scope of the present invention. As best viewed in FIGS. 4-6, oneengagement mechanism involves providing a threaded receiving aperture 12in the proximal sidewall 22 of the spinal fusion implant 10 of thepresent invention. The threaded receiving aperture 12 is dimensioned tothreadably receive a threaded connector 24 on the insertion instrument20 (as will be described in greater detail below). The receivingaperture 12 extends inwardly from the proximal side 22 in a generallyperpendicular fashion relative to the proximal side 22. Although shownas having a generally circular cross-section, it will be appreciatedthat the receiving aperture 12 may be provided having any number ofsuitable shapes or cross-sections, including but not limited torectangular or triangular. In addition to the receiving aperture 12, thespinal fusion implant 10 is preferably equipped with a pair of groovedpurchase regions 60, 61 extending generally horizontally from eitherside of the receiving aperture 12. The grooved purchase regions 60, 61are dimensioned to receive corresponding distal head ridges 62, 63 onthe insertion instrument 20 (as will be described in greater detailbelow), which collectively provide an enhanced engagement between theimplant 10 and instrument 20.

FIGS. 6-9 detail the exemplary insertion instrument 20 according to oneembodiment of the invention. The exemplary insertion instrument 20includes an elongate tubular element 28 and an inserter shaft 44. Theelongate tubular element 28 is constructed with a distal head 26 at itsdistal end, distal head ridges 62, 63 on the distal end of the distalhead 26, a thumbwheel housing 38 at its proximal end and a handle 42 atits proximal end. The elongate tubular element 28 is generallycylindrical and of a length sufficient to allow the device to span fromthe surgical target site to a location sufficiently outside thepatient's body so the handle 42 and thumbwheel housing 38 can be easilyaccessed by a clinician or a complimentary controlling device.

The elongate tubular element 28 is dimensioned to receive a spring 46and the proximal end of the inserter shaft 44 into the inner bore 64 ofthe elongate tubular element 28. The inserter shaft 44 is dimensionedsuch that the threaded connector 24 at the distal end of the insertershaft 44 just protrudes past the distal head ridges 62, 63 to allowengagement with the receiving aperture 12 of the spinal fusion implant10. It should be appreciated by one skilled in the art that such aconstruction allows the inserter shaft 44 to be able to rotate freelywithin the elongate tubular element 28 while stabilized by a spring 46to reduce any slidable play in the insertion instrument 20.

The handle 42 is generally disposed at the proximal end of the insertioninstrument 20. The handle 42 is fixed to the thumbwheel housing 38allowing easy handling by the clinician. Because the handle 42 is fixedthe clinician has easy access to the thumbwheel 34 and can stably turnthe thumbwheel 34 relative to the thumbwheel housing 38. Additionally,the relative orientation of the thumbwheel housing 38 to the handle 42orients the clinician with respect to the distal head 26 and distal headridge 62. By way of example, the thumbwheel housing 38 holds athumbwheel 34, a set screw 32, and a spacer 36. The inserter shaft 44 isattached to the thumbwheel 34 and is freely rotatable with low frictiondue to the spacer 36. One skilled in the art can appreciate myriadmethods of assembling a housing similar to the above described.

FIG. 6 details the distal head ridge of the exemplary insertioninstrument 20 coupled to the spinal fusion implant 10 through thepurchase regions 60, 61. The distal head ridges 62, 63 are dimensionedto fit slidably into the purchase regions 60, 61 with low friction toallow accurate engagement of the threaded connector 24 to the receivingaperture 12 of the spinal fusion implant 10. In the presentedembodiment, the outer dimension of the threaded connector 24 is smallerthan the largest outer dimension of the distal head 26 and elongatetubular element 28. Alternatively, other methods of creating a grippingsurface are contemplated including but not limited to knurling orfacets.

In order to use the system to perform a spinal fusion procedure, theclinician must first designate the appropriate implant size. After thespinal fusion implant 10 is chosen, the distal head ridges 62, 63 of theinserter shaft 44 are inserted into the purchase regions 60, 61 of thespinal fusion implant 10. At that time the spinal fusion implant 10 andinsertion instrument 20 are slidably engaged with one another. Beforethe clinician can manipulate the combined spinal fusion implant 10 andinsertion instrument 20, they must be releasably secured together. Inorder to secure the spinal fusion implant 10 onto the threaded connector24 of the inserter instrument 20, the clinician employs the thumbwheel34 to rotate the inserter shaft 44 and threaded connector 24. Therotation of the threaded connector 24 will releasably engage thereceiving aperture of the spinal fusion implant 10 and stabilize theinsertion instrument 20 relative to the spinal fusion implant 10.

A clinician can utilize the secured system in either an open orminimally invasive spinal fusion procedure. In either type of procedure,a working channel is created in a patient that reaches the targetedspinal level. After the creation of that channel, the intervertebralspace may be prepared via any number of well known preparation tools,including but not limited to kerrisons, rongeurs, pituitaries, andrasps. After preparation, the insertion instrument 20 is used to place aspinal fusion implant 10 into the prepared intervertebral space. Oncethe implant 10 is inserted into the prepared space, the implant 10 isreleased from the insertion instrument 20 by rotating the thumbwheel 34to disengage the threaded connector 24 from the receiving aperture 12.That motion removes the compressive force on the purchase regions 60, 61between the distal head 26 and the distal head ridges 62, 63 of thespinal fusion implant 10 and allows the insertion instrument to beslidably removed from the implant 10. After the threaded connector 24 isdisengaged from the implant 10, the insertion instrument 20 is removedfrom the working channel and the channel is closed. As previouslymentioned, additional materials may be included in the procedure before,during or after the insertion of the spinal fusion implant 10 to aid thenatural fusion of the targeted spinal level.

FIG. 10 illustrates a spinal fusion system 105 for performing spinalfusion between adjacent cervical vertebrae, including an exemplaryspinal fusion implant 110 and an exemplary cervical insertion instrument120 provided in accordance with the present invention. The spinal fusionimplant 110 may comprise of any suitable non-bone composition havingsuitable radiolucent characteristics, including but not limited topolymer compositions (e.g. poly-ether-ether-ketone (PEEK) and/orpoly-ether-ketone-ketone (PEKK)) or any combination of PEEK and PEKK.The spinal fusion implant 110 may be provided in any number of suitablesizes, such as, by way of example only, a width ranging between 11 to 14mm, a height ranging between 5 and 12 mm, and a length ranging from 14and 16 mm.

As will be described in detail below, the cervical insertion instrument120 is configured to releasably maintain the exemplary cervical fusionimplant 110 in the proper orientation for insertion. The cervical fusionimplant 110 may be simultaneously introduced into a disc space whilelocked within the cervical insertion instrument 120 and thereafterreleased. The exemplary cervical fusion implant 110, having beendeposited in the disc space, effects spinal fusion over time as thenatural bone healing process integrates and binds the implant with theadjacent vertebral bodies. This fusion may be facilitated or augmentedby introducing or positioning various materials in a space createdwithin or adjacent to the cervical fusion implant 110. Those materialsmay be introduced before, during, or after the insertion of theexemplary cervical fusion implant 110. The additional material mayinclude bone autograft harvested from the patient receiving the spinalfusion implant 10, one or more additional bone allograft,bio-resorbables or xenograft implants, any number of non-bone implants,and any number of fusion promoting compounds such as bone morphogenicprotein.

FIGS. 11-14 depict various embodiments of the exemplary cervical fusionimplant 110. Some common attributes are shared among the variousembodiments. More specifically, each cervical fusion implant 110 has atop surface 31, a bottom surface 33, lateral sides 14, a proximal side22, and a distal side 16. In one embodiment, the top and bottom surfaces31, 33 are generally parallel. It can be appreciated by one skilled inthe art that although the surfaces are generally parallel, that the top31 and bottom 33 surfaces may be angled with respect to one another tomatch the natural curve of the spine (i.e. lordosis or kyphosis). By wayof example, implants for the cervical or lumbar regions of the spinewill have anterior height greater than the posterior height to match thenatural lordosis in those regions. Inversely, the implants designed forimplantation into the thoracic region will be manufactured with aposterior height greater than the anterior height to match the naturalkyophosis in that region. Additionally, the angled surface can aid inoverall fit within the vertebral disc space.

The cervical fusion implant 110 preferably includes two receivingapertures 12 which are centrally aligned on the proximal side 22. Thereceiving apertures 12 extend inwardly from the proximal side 22 in agenerally perpendicular fashion relative to the proximal side 22.Although shown as having a generally circular cross-section, it will beappreciated that the receiving aperture 12 may be provided having anynumber of suitable shapes or cross-sections, including but not limitedto rectangular or triangular.

The exemplary cervical fusion implant 110 also preferably includesanti-migration features such as anti-migration teeth 6 along the topsurface 31 and bottom surface 33. Additional anti-migration features mayinclude a plurality of proximal anti-migration spikes 68 and/or distalanti-migration spikes 70 integrated vertically through the cervicalfusion implant 110. The anti-migration features increase the frictionbetween the cervical fusion implant 110 and the adjacent contactingsurfaces of the vertebral bodies. That friction prohibits migration ofthe cervical fusion implant 110 during the propagation of natural bonyfusion. It should be appreciated by one skilled in the art that suchanti-migration teeth 6 can be oriented in a any manner other thangenerally vertically (as shown) without departing from the scope of thepresent invention. Moreover, as described above, the spikes 68, 70 maybe constructed from any of a variety of radiopaque materials, includingbut not limited to a metal, ceramic, and/or polymer material. When thespike elements 68, 70 are provided having such radiodensecharacteristics, and the implant 110 is manufactured from a radiolucentmaterial (such as, by way of example only, PEEK and/or PEKK), the spikeelements 68, 70 will be readily observable under X-ray or fluoroscopysuch that a surgeon may track the progress of the implant 110 duringimplantation and/or the placement of the implant 110 after implantation.

The cervical fusion implant 110 has one large fusion aperture 2,extending in a vertical fashion through the top surface 31 and bottomsurface 33 which will function primarily as the avenue for bony fusionbetween adjacent vertebrae. The cervical fusion implant 110 may have aplurality of visualization apertures 4 which can also serve as an avenueof bony fusion on the lateral sides 14 via cell migration or additionaladjuvants. The visualization apertures 4 serve an additional function ofallowing a clinician to make visual observations of the degree of bonyfusion un-obscured by the lateral side 14 to facilitate furtherdiagnosis and treatment.

FIG. 15 illustrates, by way of example, the orientation of the cervicalfusion implant 110 prior to attachment to the cervical insertioninstrument 120 by a clinician. One skilled in the art would appreciatethat although the current embodiment shows a slidable engagement,various other methods of engagement are contemplated, such as,threadable or hooking features.

FIGS. 16-17 detail the tubular lock member 21 of the exemplary cervicalinserter instrument 110. The tubular lock member 21 includes a centralbore 25 dimensioned to receive the proximal end of the elongate forkmember 11 therein. The internal dimension of the central bore 25 issmaller than the largest freestanding outer dimension of the taperfeature 19. As a result, the portion of the elongate fork member 11 thatmay be received by the central bore 25 of the tubular lock member 21 islimited by interference between the distal end of the tubular lockmember 21 and the taper feature 19 of the elongate fork member 11. Inthe present embodiment, the outer dimension of the threaded feature 13of the elongate fork member 11 is smaller than the largest outerdimension of the taper feature 19 on the elongate fork member 11. Athread feature 23 (not shown) at the proximal end of the tubular lockmember 21 is situated inside the central bore 25. The thread feature 23matches the thread feature 13 on the elongate fork member 11 so thatthey can be threadably attached to one another. To ease the rotation ofthe tubular lock member 21 by hand, two semi-circular wings 27 may beprovided protruding laterally outward from either side of the tubularlock member 21. Alternatively, other methods of creating a grippingsurface are contemplated including but not limited to knurling orfacets.

A clinician can utilize the secured system in either an open orminimally invasive spinal fusion procedure. In either type of procedure,a working channel is created in a patient that reaches the targetedspinal level. After the creation of that channel, the intervertebralspace would be prepared (via known instruments as described above).After preparation, the insertion instrument 120 is used to place acervical fusion implant 110 into the prepared intervertebral space. Oncethe cervical fusion implant 110 is inserted into the prepared space, theimplant 110 is released from the cervical insertion instrument 120 byretracting the tubular lock member 21 from the elongate fork member 11by rotating the tubular lock member 21 with respect to the elongate forkmember 11 in the opposite direction from that used to initially securethe implant 110. That motion removes the compressive force on thepurchase region 39 between the apertures 12 of the cervical fusionimplant 110 and allows the engagement features 17 to be slidably removedfrom the apertures 12. After the engagement features 17 are disengagedfrom the cervical fusion implant 110, the cervical inserter instrument120 is removed from the working channel and the channel is closed. Aspreviously mentioned, additional materials may be included in theprocedure before, during or after the insertion of the cervical fusionimplant 110 to aid the natural fusion of the targeted spinal level.

In order to use the system to perform a spinal fusion procedure, theclinician must first designate the appropriate implant size. After thecervical fusion implant 110 is chosen, the engagement features 17 of theelongate fork member 11 are inserted into the apertures 12 on theimplant 110. At that time the cervical fusion implant 110 and elongatefork member 11 are slidably engaged with one another. Before theclinician can manipulate the combined cervical fusion implant 110 andelongated fork member 11, they must be releasably secured together. Inorder to secure the cervical fusion implant 110 onto the elongate forkmember 11, the clinician would next employ the tubular lock member 21.The clinician would insert the proximal end of the elongate fork member11 into the central bore 25 of the tubular lock member 21 at its distalend. The tubular lock member 21 would then be advanced over the elongatefork member 11 until the thread feature 13 of that member and the threadfeature 23 of the tubular lock member 21 become engaged.

Once engaged, advancement of the tubular lock member requires rotationof the tubular lock member 21 with respect to the elongate fork member11. Preferably, after only a small amount of engagement of the threadfeatures the distal end of the tubular lock member 21 would contact thetaper feature 19 of the elongate fork member 11. The tubular lock member21 would be advanced creating greater interference as the distal endapproaches the distal end of the taper feature 19 which has the largerouter dimension. The increasing interference would laterally displacethe clamping arms 15 of the elongate fork member 11 towards each other.Since the engagement features 17 of the elongate fork member 11 wereinitially inserted into the apertures 12 of the exemplary cervicalfusion implant 110, the displacement of the clamping arms 15 wouldcreate a compressive force on the purchase region 39 separating theapertures 12 of the exemplary cervical fusion implant 110. Thatcompressive force allows a clinician to manipulate the system withoutthe exemplary cervical fusion implant 110 becoming disengaged from thecervical inserter instrument 120.

The enhanced visualization features of the implants 10, 110 areexplained in greater detail with reference to FIGS. 18-23. FIG. 18illustrates an implant 10 dimensioned particularly for use in aposterior approach (PLIF) having (by way of example only) a widthranging between 9 and 11 mm, a height ranging between 8 and 14 mm, and alength ranging between 25 and 30 mm. FIG. 19 illustrates the implant 10of FIG. 18 from a side perspective via as taken via X-ray or fluoroscopytechniques, clearly showing the location of the spike elements 7 and 8(there is no central spike element 9 as with FIG. 1) relative to theimplant 10 and visualization apertures 4. FIG. 20 illustrates an implant10 dimensioned particularly for use in a lateral approach (XLIFTM byNuVasive) having (by way of example only) a width of approximately 18mm, a height ranging between 8 and 16 mm, and a length ranging between40 and 45 mm. FIG. 21 illustrates the implant 10 of FIG. 20 from a sideperspective via as taken via X-ray or fluoroscopy techniques, clearlyshowing the location of the spike elements 7, 8, 9 relative to theimplant 10 and visualization apertures 4. FIG. 22 illustrates an implant110 dimensioned particularly for use in the cervical spine having (byway of example only) a width of approximately 11 mm, a height rangingbetween 5 and 12 mm, and a length of approximately 14 mm. FIG. 23illustrates the implant 110 of FIG. 22 from a side perspective via astaken via X-ray or fluoroscopy techniques, clearly showing the locationof the spike elements 66 relative to the implant 110 and visualizationapertures 4. In this fashion, a surgeon may easily track the progress ofthe implant 10, 110 during implantation and/or after implantation byvisualizing the spike elements 7,8,9 and 66, respectively, under X-rayand/or fluoroscopy according to the present invention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

For example, while described herein primarily with reference to thelumbar and cervical spinal surgery, it is to be readily appreciated thatthe spinal fusion implants of the present invention may be suitable foraccomplishing fusion in the thoracic spine without departing from thescope of the present invention. Moreover, it is to be readilyappreciated that the insertion tools described herein may be employedwith implants of any number of suitable constructions, including but notlimited to metal, ceramic, plastic or composite.

1. A spinal fusion implant of non-bone construction positionable withinan interbody space between a first vertebra and a second vertebra, saidimplant comprising: an upper surface including anti-migration elementsto contact said first vertebra when said implant is positioned withinthe interbody space, a lower surface including anti-migration elementsto contact said second vertebra when said implant is positioned withinthe interbody space, a distal wall, a proximal wall, a first sidewall,and a second sidewall generally opposite from the first sidewall,wherein said distal wall, proximal wall, first sidewall, and secondsidewall comprise a radiolucent material; wherein said implant has alongitudinal length extending from a proximal end of said proximal wallto a distal end of said distal wall, said implant has a maximum lateralwidth extending from said first sidewall to said second sidewall along amedial plane that is generally perpendicular to said longitudinallength, and said longitudinal length is greater than said maximumlateral width; at least a first fusion aperture extending through saidupper surface and lower surface and configured to permit bone growthbetween the first vertebra and the second vertebra when said implant ispositioned within the interbody space, said first fusion aperturehaving: a longitudinal aperture length extending generally parallel tothe longitudinal length of said implant, and a lateral aperture widthextending between said first sidewall to said second sidewall, whereinthe longitudinal aperture length is greater than the lateral aperturewidth; and at least first and second radiopaque markers orientedgenerally perpendicular to said longitudinal length of said implant,wherein said first radiopaque marker extends into said first sidewall ata position proximate to said medial plane, and said second radiopaquemarker extends into said second sidewall at a position proximate to saidmedial plane.
 2. The spinal fusion implant of claim 1, wherein the firstand second radiopaque markers are substantially equally spaced apartfrom said proximal end of said proximal wall by a first longitudinaldistance.
 3. The spinal fusion implant of claim 1, further comprising athird radiopaque marker that extends into said distal wall, and a fourthradiopaque marker that extends into said proximal wall.
 4. The spinalfusion implant of claim 3, wherein said third radiopaque marker extendsentirely through a height of said distal wall, and wherein said fourthradiopaque marker extends entirely through a height of said proximalwall.
 5. The spinal fusion implant of claim 1, further including atleast one receiving aperture position is said proximal wall.
 6. Thespinal fusion implant of claim 5, wherein said threaded receivingaperture is configured to releasably mate with an inserter tool.
 7. Thespinal fusion implant of claim 6, wherein said receiving aperturecomprises a threaded receiving aperture extending into said proximalwall and having a central axis generally parallel to said longitudinallength of said implant.
 8. The spinal fusion implant of claim 7, furthercomprising a pair of lateral grooves positioned in said proximal walland extending laterally of said threaded receiving aperture.
 9. Thespinal fusion implant of claim 1, wherein said maximum lateral width ofsaid implant is approximately 18 mm.
 10. The spinal fusion implant ofclaim 1, wherein said radiolucent material comprises PEEK.
 11. Thespinal fusion implant of claim 1, wherein said implant includes at leastone visualization aperture extending through at least one of said firstsidewall and said second sidewall.
 12. The spinal fusion implant ofclaim 1, wherein said upper and lower surfaces are generally parallel toone another.
 13. The spinal fusion implant of claim 1, wherein saidupper and lower surfaces are generally angled relative to one another toapproximately correspond to lordosis of a lumbar spine when said implantis positioned within the interbody space.
 14. The spinal fusion implantof claim 1, wherein said first fusion aperture is one of generallyrectangular and generally oblong in shape.
 15. The spinal fusion implantof claim 1, further comprising a medial support extending between thefirst and second sidewalls
 16. The spinal fusion implant of claim 15,wherein said medial support is positioned along said medial plane. 17.The spinal fusion implant of claim 1, further including a second fusionaperture extending through said upper surface and lower surface andconfigured to permit bone growth between the first vertebra and thesecond vertebra when said implant is positioned within the interbodyspace.
 18. The spinal fusion implant of claim 17, wherein said secondfusion aperture is separated from said first fusion aperture by a medialsupport.
 19. The spinal fusion implant of claim 1, wherein saidanti-migration elements of said upper surface comprise a plurality ofridges.
 20. The spinal fusion implant of claim 19, wherein saidplurality of ridges extend generally perpendicular to said longitudinallength.
 21. The spinal fusion implant of claim 1, wherein saidanti-migration elements of said upper surface comprise spike elements.22. The spinal fusion implant of claim 21, wherein said spike elementsprotrude to pointed tips configured to engage said first vertebra. 23.The implant of claim 1, wherein said maximum lateral width of saidimplant is greater than a lateral width of the distal end of said distalwall and is greater than a lateral width of the proximal end of saidproximal wall.
 24. The implant of claim 1, wherein said implant has aheight extending from said upper surface to said lower surface, whereinsaid maximum lateral width is greater than said height.
 25. The spinalfusion implant of claim 1, wherein the lateral aperture width of saidfirst fusion aperture is more than two time greater than a lateralthickness of said first sidewall and is more than two time greater thana lateral thickness of said second sidewall.
 26. The spinal fusionimplant of claim 1, wherein said elongate body of at least one of saidradiopaque markers is shorter than an implant height extending from saidupper surface to said lower surface.
 27. The spinal fusion implant ofclaim 1, further comprising an osteoinductive material positioned withsaid first fusion aperture.
 28. A method of introducing a spinal fusionimplant of non-bone construction via a lateral trans-psoas surgicalapproach, the method comprising: preparing an intervertebral disc spacefor receiving a spinal fusion implant; releasably attaching the spinalfusion implant to an inserter tool, a distal end portion of the insertertool having a threaded connector that threadably engages with a threadedreceiving aperture positioned in a proximal wall of the spinal fusionimplant, wherein the spinal fusion implant has a maximum longitudinallength extending from a proximal end of the proximal wall to a distalend of a distal wall; inserting the spinal fusion implant into theintervertebral disc space via a lateral, trans-psoas path to theintervertebral disc space, the spinal fusion implant comprising an uppersurface including anti-migration elements to contact a first vertebraadjacent to the intervertebral disc space, a lower surface includinganti-migration elements to contact a second vertebra adjacent to theintervertebral disc space, the distal wall, the proximal wall, ananterior sidewall to face an anterior aspect of the intervertebral discspace, and a posterior sidewall to face a posterior aspect of theintervertebral disc space, each of the distal wall, proximal wall, firstsidewall, and second sidewall comprising a radiolucent material, whereinthe spinal fusion implant further comprises at least three radiopaquemarkers having elongate bodies oriented generally perpendicular to themaximum longitudinal length of the implant, wherein a first of the atleast three radiopaque markers extends into the distal wall, a second ofthe at least three radiopaque markers extends into the proximal wall,and a third of the at least three radiopaque markers extends into acentral region of the spinal fusion implant including portions of theanterior and posterior sidewalls positioned generally centrally betweenthe proximal wall and the distal wall.
 29. The method of claim 28,further comprising releasing the spinal fusion implant from the insertertool.
 30. The method of claim 29, wherein the spinal fusion implant isreleased from the inserter tool by rotating a first component of theinserter tool positioned along a proximal portion of the inserter toolrelative to a second component of the inserter tool.
 31. The method ofclaim 29, wherein the first component of the inserter tool rotatestogether with the threaded connector at the distal end portion of theinserter tool, and wherein the second component of the inserter toolincludes head protrusions at the distal end portion of the insertertool, the head protrusions being configured to mate with lateral groovespositioned in the proximal wall of the spinal fusion implant.
 32. Themethod of claim 28, wherein the inserter tool has a longitudinal lengththat is more than four times greater than the maximum longitudinallength of the spinal fusion implant.
 33. The method of claim 28, furthercomprising establishing a working corridor to a targeted spinal site soas to define the lateral, trans-psoas path to the intervertebral discspace.
 34. The method of claim 33, wherein the step of preparing theintervertebral disc space includes introducing one or more preparationtools via the working corridor, the preparation tools including one ormore of kerrisons, rongeurs, pituitaries, and rasps.
 35. The method ofclaim 28, further comprising positioning an osteoinductive materialwithin at least a first fusion aperture of the spinal fusion implantextending through the upper surface and the lower surface, the firstfusion aperture having: a longitudinal aperture length extendinggenerally parallel to the maximum longitudinal length of the implant,and a lateral aperture width extending between the anterior sidewall tothe posterior sidewall, wherein the longitudinal aperture length isgreater than the lateral aperture width.
 36. The method of claim 35,further comprising positioning the osteoinductive material within asecond fusion aperture of the spinal fusion implant, the second fusionaperture extending through said upper surface and lower surface, and thesecond fusion aperture being separated from the first fusion aperture bya medial support.
 37. The method of claim 28, further comprising using amedical imaging technique to view the first, second, and thirdradiopaque markers of the spinal infusion implant in an individual imageafter inserting the spinal fusion implant into the intervertebral discspace via the lateral, trans-psoas path.
 38. The method of claim 28,wherein at least a portion of the central region defining a maximumlateral width of the spinal fusion implant extending from the anteriorsidewall to the posterior sidewall, wherein the maximum longitudinallength of the implant is at least two and half times greater than themaximum lateral width.
 39. The method of claim 38, wherein the maximumlateral width of the implant is greater than a lateral width of thedistal end of the distal wall and is greater than a lateral width of theproximal end of the proximal wall.
 40. The method of claim 38, whereinthe maximum lateral width of said implant is approximately 18 mm. 41.The method of claim 28, wherein the spinal fusion implant inserted intothe intervertebral disc space includes at least a first fusion apertureextending through the upper surface and lower surface for permittingbone growth between the first vertebra and the second vertebra, thefirst fusion aperture having: a longitudinal aperture length extendinggenerally parallel to the maximum longitudinal length of the implant,and a lateral aperture width extending between the anterior sidewall andthe posterior sidewall, wherein the longitudinal aperture length isgreater than the lateral aperture width.
 42. The method of claim 28,wherein the spinal fusion implant inserted into the intervertebral discspace includes a fourth radiopaque marker, the fourth radiopaque markerhaving an elongate body oriented generally perpendicular to the maximumlongitudinal length of the implant, the fourth radiopaque markerextending into the central region at a position spaced apart from thethird radiopaque marker.
 43. The method of claim 28, wherein the spinalfusion implant inserted into the intervertebral disc space comprisessaid radiolucent material of PEEK.
 44. The method of claim 28, whereinthe spinal fusion implant inserted into the intervertebral disc spaceincludes one or more visualization aperture extending through at leastone of said first sidewall and said second sidewall
 45. The method ofclaim 28, wherein the spinal fusion implant inserted into theintervertebral disc space includes a medial support extending betweenthe anterior and posterior sidewalls.
 46. The method of claim 45,wherein the medial support is positioned along the central region.